Verwing: I have never seen a per-cat for sale by itself, only as a complete assembly. I am not sure if the per-cat gets clogged-up like the cat or not....no idea of what a pre-cat internals are compared to a cat. I would suggest replacing the entire assembly. Yes I know a bit costly, but it would be done and over with.

I was going to replace just the cat on my '02, but since I am not a welder I would have to take it to a shop and also buy their replacement cat and I thought I would replace O2 sensors at the same time....it was cheaper to do it myself and I could do the repair on my own schedule....on a weekend instead of taking time off of work....so that is what I did. I too did not want a one piece welded system.

RockAuto has the Walker assembly for a good price, be sure to find a 5% coupon, and also get the O2 sensors from them since yours have seen too much fuel; or if you want I could send you two of the three O2 sensors that I removed from my '02...I messed one of them up getting it out...the other two were working fine...have 95k miles on them, would save you some $$$ at this time....just let me know on this.

 

Thanks again guys. I'm going to research this today and decide what to do.

 

I just had somebody on this forum save my behind with this the other day.. for the coolant leak, check the bottom of the upper radiator hose. Mine wore through right on top of the EGR tube and made it look like a bad LIM to my highly untrained eye. :-)

 

The pre-converter can overheat, meltdown & clog just like any converter. 2001 requires 2 converters, (that's why they're there). If you eliminate the pre-converter, the downstream converter will overheat, meltdown and clog, guaranteed. This is why it's replaced as an assembly and includes both converters, (the "Y" pipe is not available seperately).

 

My friend from car dealership that got me the spider injection came through again with an aftermarket cat. I first cut the existing rear cat off and started Blazer to see it pre-cat was clogged also, and needed replacing. It wasn't, and engine ran well, so I dropped remaining pipe to muffler, welded cat to it as well as an adaptor to the new cat inlet that let me slide it over and clamp to pipe coming from pre-cat. All sensors and hangers are in their original location, Blazer is running really well, and no codes are popping up after a 15-20 minute drive.

Large leak turned out to be small hose coming off top of water pump/engine connection. I'll have to take the rap for that because I just changed water pump. Other than that, car appears good to go and ready for another couple hundred thousand miles.

I want to thank all of you that provided me with guidance, tips, and info on how to go about getting this done. My son had given up on this vehicle, and I must admit, I had some doubts myself that maybe this trucks best days were behind it. You guys were right though, this truck has plenty of life left in it, and both my son and I could not be any happier! Thanks again to all! Mike

 

I wanna ask why it would overheat. You know alot more then i do lol. i guess im asking whats different with the 01 compared to say a 96? just about same everything,same heads,cam,block etc. (other then small differences of course with electrical,trans etc. Im a lil tipsy,i guess this doesn't make sense to me right now. thanks chuck!

glad you got it figured out. i wish more people would post back.

 

One of the things that the converter does is store oxygen. The dirtier an engine runs, (emission wise) the more capacity the converters need to have in order to store up enough oxygen. If they can't store enough, the unburned fuel in the exhaust causes the converter to overheat. Same end result when you have a misfire: extremely rich mixture, and not enough oxygen. The substrate, (honeycomb looking material) gets cherry red hot and melts down into a solid blob, literally looks & feels like a rock. Once this happens, the converter is destroyed. There is no fix other than replace it. It can happen gradually over miles of driving, or in a very short period of time. It just depends on how overly rich the mixture is, and for how long. If memory serves correct, a good exhaust system will have less than one half psi of backpressure, (virtually nothing). As the converter deteriorates, backpressure will increase and the engine will become "constipated" and lose power. Much like a cork in your sphincter: eventually the pressure builds up and something bad is going to happen

The number of, or size, of the converters is determined by what emission control devices the engine is equipped with to clean up the exhaust: secondary air pump, EGR valve, axle ratios, 4WD, GVW, transmission, etc, and how the PCM is programmed. The cleaner the engine burns, the less it needs in the way of converters. 96 & 97 don't have secondary air pumps but they both have 4 converters. 98 doesn't have an air pump either, but it only has one converter. The 4.3L "X" engine, (2002 and newer) has the upgraded injectors, no poppet valves, no EGR valve, no air pump, and it has 2 converters.


EDIT: One way the manufacturers can "cut corners" is with the secondary air pump. It pumps oxygen into the exhaust to help the converter. By doing that, they can get away with using a smaller converter. Beware if the air pump system fails, the converter is vulnerable to failure.